Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281735 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1235 PM EST SAT FEB 28 2015 .SYNOPSIS... COLD HIGH PRESSURE WILL WEDGE SOUTH ALONG THE EASTERN SLOPES OF THE APPALACHIANS TODAY AND PERSIST INTO SUNDAY. OUR NEXT WEATHER SYSTEM WILL BRING A LIGHT WINTRY MIX TO THE AREA SUNDAY INTO MONDAY. TEMPERATURES WILL MODERATE THROUGH THE MIDDLE OF THE WEEK...PRIOR TO THE PASSAGE OF A STRONG COLD FRONT WEDNESDAY INTO THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1033 AM EST SATURDAY... WITH SOME SUNSHINE AND TEMPERATURES WARMING ABOVE FREEZING...DECIDED TO CANCEL WINTER WEATHER ADVISORY FOR BLACK ICE ACROSS NORTH CAROLINA. NUDGED HIGH TEMPERATURES UP A FEW DEGREES FOR THIS AFTERNOON IN THE SOUTHEAST. AS OF 916 AM EST SATURDAY... A 1044 MB SURFACE HIGH PRESSURE CENTERED OVER PENNSYLVANIA WILL PUSH SOUTH INTO OUR REGION TODAY INTO TONIGHT. MADE SOME MINOR ADJUSTMENTS IN TEMPERATURES FOR THIS MORNING INTO THIS AFTERNOON. WILL WAIT FOR THE 12Z MODEL RUN BEFORE MAKING ANY ADJUSTMENTS TO TONIGHT FORECAST WITH THE RETURN MOISTURE AS THE HIGH SLIDES EAST. MORE CHANGES LATER... AS OF 230 AM EST SATURDAY... DEVELOPING WEDGE DOWN THE EASTERN SLOPES OF THE MOUNTAINS THE MAIN ISSUE OVER THE NEXT 24 HOURS AS ARCTIC HIGH PRESSURE SLIDES SE FROM THE MID ATLANTIC STATES TODAY TO ALONG THE EASTERN SEABOARD OVERNIGHT. THIS WILL CREATE MORE OF AN EASTERLY COMPONENT TO THE LOW LEVEL FLOW TODAY ALLOWING SOME LOW LEVEL MOISTURE TO WORK WESTWARD UNDER THE INVERSION WHILE BEING TOPPED BY SHEARED HIGH/MID LEVEL CLOUDINESS FROM DAMPENING SHORTWAVE ENERGY TO THE WEST. GIVEN SUCH LOW DEWPOINTS DOESN`T APPEAR THAT THE MOISTURE WILL EVER GET DEEP ENOUGH TO PRECIPITATE ANYTHING MORE THAN SPOTTY FLURRIES/DRIZZLE OUT EAST TODAY SO LEAVING POPS OUT FOR NOW. HOWEVER CLOUDS REMAIN TRICKY WITH POTENTIAL TO SEE A LOW CLOUD CANOPY GET LOCKED IN ALONG/EAST OF THE BLUE RIDGE TODAY WITH MORE MID DECK OVER THE WEST. THIS MAY SPELL AN EVEN COLDER DAY THAN WHAT MOS SHOWS ESPCLY WHERE STARTING OFF IN THE SINGLE DIGITS AND TEENS. THEREFORE LEANING TOWARD MORE CLOUDS THROUGH THE AFTERNOON AND HIGHS CLOSER TO THE COLDER MAV MOS OUTSIDE OF THE SOUTHEAST WHERE THE MET LOOKS BETTER PER STARTING OUT A BIT WARMER UNDER LOW CLOUDS ALREADY. PARENT SURFACE HIGH WILL SLOWLY WEAKEN OVERNIGHT WITH THE LOW LEVEL TRAJECTORY TURNING MORE SOUTHEAST OVER THE WEST WHERE MOST MODELS CONTINUE TO SHOW AN AXIS OF RETURN MOISTURE RUNNING UP INTO THE SW ZONES LATE. NAM CONTINUES TO BE THE WETTEST AS TYPICAL WITH RETURN FLOW ISENTROPIC LIFT TYPE SITUATIONS...WHILE THE EC/CMC REMAIN BASICALLY DRY...AND THE GFS IN BETWEEN PLUS SLIGHTLY SLOWER. GIVEN PAST EVENTS WILL TREND TOWARD THE NAM TIMING BUT WITH QUITE LESS QPF WHICH WILL BE RUNNING INTO RESIDUAL COLD/DRY AIR THAT WILL BE RETREATING AS STEADY WARMING ALOFT KICKS IN. THIS SCENARIO UNDER A DEVELOPING WARM NOSE ALOFT WOULD PERHAPS BRING SOME LIGHT FREEZING RAIN/SLEET INTO PARTS OF NW NORTH CAROLINA LATE WITH A LIGHT WINTRY MIX SPREADING UP ALONG THE SOUTHERN BLUE RIDGE AND POINTS EAST OF BCB/ROA BY DAYBREAK. HOWEVER WONT GO HIGHER THAN LOW CHANCE TO SLIGHT POPS FOR NOW...BUT INCLUDE A MENTION IN THE HWO OVER THE SOUTH/SW LATE FOR AT LEAST SPOTTY ICING GIVEN FORECAST SURFACE WET BULBS STILL BELOW FREEZING. OTHERWISE MAINLY CLOUDY MOST SPOTS WITH EARLY LOWS...MOSTLY 20S...STEADYING OR SLOWLY RISING AFTER MIDNIGHT WITHIN THE SURFACE-85H WEAK WARM ADVECTION REGIME. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... AS OF 330 AM EST SATURDAY... COMPLICATED FORECAST THROUGH THE SHORT TERM. GUIDANCE HAD TRENDED TOWARD THE FASTER NAM AND PRECIPITATION LOOKS TO ARRIVE IN THE AREA SUNDAY MORNING WITH GOOD ISENTROPIC LIFT AS WARM SWLY WINDS RUN OVER THE TOP OF THE COLD AIR WEDGE. SPEAKING OF THE WEDGE...BELIEVE THIS WILL BE A TOUGH NUT TO CRACK WITH VERY COLD ANTECEDENT CONDITIONS AND A SNOW PACK TO REINFORCE THE COLD AIR. HAVE TRENDED THE TEMP FORECAST DOWN EAST OF THE BLUE RIDGE. AS IS USUALLY THE CASE...EXPECT TEMPS WEST TO SLOWLY RISE THROUGH SUNDAY AND CONTINUE RISING INTO SUNDAY NIGHT. AREAS TO THE EAST WILL RISE EVER SO SLOWLY DURING THE DAY ON SUNDAY BUT EXPECT A SURGE IN TEMPS LATE SUNDAY NIGHT INTO MONDAY AS THE APPROACHING COLD FRONT FINALLY BOOTS THE WEDGE OUT. THIS MEANS WESTERN AREAS WILL BE LOOKING AT A MIX OF FREEZING RAIN AND SLEET SUNDAY MORNING THEN GOING TO RAIN BY THE AFTERNOON. NORTHERN AND EASTERN AREAS WILL BE LOOKING AT MAINLY FREEZING RAIN AND SLEET...AND THE PRECIPITATION WILL LIKELY END BEFORE IT HAS A CHANCE TO CHANGE OVER. THE UPSIDE IS THAT THIS LOOKS LIKE A LOW QPF EVENT SO WHILE FREEZING RAIN AND A GLAZE OF ICE WILL BE FAIRLY WIDESPREAD IT WILL BE UNDER ONE TENTH OF AN INCH. AS COLDER AIR MOVES IN WITH THE FRONT WE WILL SEE UPSLOPE SNOW SHOWERS WITH SOME MINOR SLUSHY ACCUMULATIONS OF AN INCH OR LESS ACROSS THE FAR WESTERN SLOPES LATE SUNDAY NIGHT INTO MONDAY MORNING. THINGS QUIET DOWN AS HIGH PRESSURE BUILDS IN MONDAY AFTERNOON WITH GUSTY NORTHWEST WINDS. HOWEVER...OUR REPRIEVE WILL BE SHORT LIVED AS THE NEXT SYSTEM WILL BE APPROACHING FROM THE WEST AND SPREAD PRECIPITATION BACK INTO THE AREA TUESDAY MORNING. THIS LOOKS LIKE ANOTHER WEDGE SCENARIO WITH MIXED PRECIPITATION BUT DETAILS ARE SKETCHY AT THIS POINT SO WILL BE LOOKING TO LATER MODEL RUNS TO SEE HOW THE SITUATION EVOLVES. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... AS OF 315 PM EST FRIDAY... TUESDAY NIGHT LOWS WILL FALL INTO THE UPPER 30S AND LOW 40S MOST LOCATIONS. BY WEDNESDAY MORNING...THE LOW PRESSURE SYSTEM WILL BE LOCATED OVER SOUTHERN CANADA...AND WILL DRAG A STRONG COLD FRONT TOWARD THE APPALACHIAN CHAIN. FORECAST MODELS VARY IN THE TIMING OF THE FRONT`S ARRIVAL INTO OUR AREA...WITH THE GENERAL CONSENSUS LEANING TOWARD THE FRONT REACHING OUR SOUTHEAST WEST VIRGINIA COUNTIES DURING THE EVENING. AS SUCH...EXPECT WEDNESDAY TEMPERATURES TO BE THE WARMEST WE HAVE SEEN IN WEEKS...WITH HIGHS RANGING FROM THE LOW/MID 50S FOR THE MOUNTAINS...AND THE UPPER 50S TO MID 60S FOR THE PIEDMONT. ATMOSPHERIC MOISTURE ACROSS OUR AREA AHEAD OF THE FRONT WILL BE SIGNIFICANTLY ABOVE NORMAL FOR EARLY MARCH...SO WILL BE KEEPING OUR EYE ON THE POTENTIAL FOR WIDESPREAD HEAVY RAIN FOR WEDNESDAY EVENING/WEDNESDAY NIGHT...ESPECIALLY IF THE COLD FRONT BECOMES STALLED ACROSS OUR AREA AS SOME MODELS SUGGEST. WHILE WE SHOULD SEE A SIGNIFICANT REDUCTION IN THE SNOWPACK ACROSS OUR AREA BEFORE THE HEAVY PRECIPITATION ARRIVES...EXPECT THERE WILL STILL BE AREAS OF FROZEN GROUND DUE TO THE PROLONGED COLD WEATHER OF RECENT WEEKS... WHICH WILL CAUSE MUCH OF THE RAIN TO TRANSLATE DIRECTLY INTO RUNOFF RATHER THAN SOAK INTO THE GROUND. WILL CONTINUE TO MONITOR THE EVOLUTION OF THIS SYSTEM THROUGH THE WEEKEND FOR THE POTENTIAL OF FLOODING WEDNESDAY NIGHT. THE COLD FRONT WILL REPRESENT THE LEADING EDGE OF YET ANOTHER ARCTIC AIRMASS...WHICH WILL ADVANCE FROM THE CENTRAL PLAINS UP THE OHIO RIVER VALLEY ON THURSDAY. DOWNSLOPE NORTHWESTERLY FLOW WILL LEAD TO DRYING CONDITIONS AND DIMINISHING CLOUD COVER ACROSS OUR AREA...WITH AFTERNOON HIGHS RANGING FROM THE 30S WEST TO THE 40S EAST. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 1235 PM EST SATURDAY... AS HIGH PRESSURE IN PENNSYLVANIA WEDGES SOUTH INTO OUR REGION...EASTERLY FLOW EXPECTED THIS AFTERNOON INTO TONIGHT. VFR CONDITIONS WILL LOWER TO MVFR THIS EVENING INTO TONIGHT. MID AND HIGH CLOUDS WILL INCREASE ABOVE THE TRAPPED LOW LEVEL MOISTURE IN ADVANCE OF AN APPROACHING COLD FRONT. THE LOW LEVEL WIND FLOW WILL CONTINUE TO VEER SOUTHEASTERLY ACROSS THE MOUNTAINS AND EASTERLY ACROSS THE PIEDMONT AS THE CENTER OF HIGH PRESSURE SHIFTS OFF THE NEW ENGLAND COAST. PRECIPITATION WILL BEGIN TO MOVE INTO THE AREA LATE TONIGHT...STARTING OFF AS BRIEF SNOW/SLEET FOR MANY LOCATIONS BUT GRADUALLY CHANGING OVER TO FREEZING RAIN AS WARM AIR ALOFT BUILDS NORTHWARD ALONG THE APPALACHIAN CHAIN. A WINTRY MIXTURE WILL TRANSITION TO FREEZING RAIN AND RAIN ON SUNDAY. AS TEMPERATURES WARM ABOVE FREEZING FROM SOUTH TO NORTH DURING AFTERNOON SUNDAY...CAUSING ALL FREEZING PRECIPITATION TO CHANGE OVER TO RAIN. MVFR/ IFR CEILINGS AND REDUCTIONS IN VISIBILITY DUE TO PRECIPITATION ARE EXPECTED AREAWIDE. MEDIUM CONFIDENCE ON CEILINGS...VISIBILITIES AND WINDS DURING THE PERIOD. A SHARP COLD FRONT WILL CROSS THE AREA MONDAY AFTERNOON WITH NORTHWEST WINDS INCREASING. ON THE HEELS OF THE SUNDAY/MONDAY SYSTEM WILL BE YET ANOTHER POTENTIALLY POTENT SYSTEM THAT MAY IMPACT ALL OR PARTS OF THE REGION TUESDAY INTO WEDNESDAY WITH SUB-VFR DEVELOPING IN MOST LOCATIONS LATER TUESDAY INTO WEDNESDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...DS/JH NEAR TERM...JH/KK SHORT TERM...MBS LONG TERM...NF AVIATION...JH/KK

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